How are significant figures determined if a number is expressed in scientific notation?
The same rules (see below) apply whether a number is expressed in long form or in scientific notation.
Rules for significant figures:
1. Non-zero digits are ALWAYS significant
2. Zeroes between other significant figures are significant
3. Significant figures begin with the left-most non-zero digit
4. The rightmost digit (of a decimal number – one with an expressed decimal point) is significant (even if it is a zero)
5. If there is no decimal point then the right-most non-zero digit is the least significant digit